Even though you may not begin counting the clean days until five days have elapsed since the onset of the niddah status, you may perform the hefsek taharah sooner than day five if the bleeding has stopped. The hefsek taharah need not be performed immediately prior to starting the clean days (see our article on timing of hefsek taharah).

Therefore, your hefsek taharah from Monday remains valid, but the earliest you may begin counting the clean days is on Wednesday. As long as you performed a bedikah on Wednesday, that counts as day one of your seven clean days, and your scheduled immersion would be Tuesday night.

Even though you were out of town on Thursday, your five day minimum only began on Friday when you were rendered niddah. Therefore, the earliest you could have begun your seven clean days was on Wednesday.

Please feel free to get back to us with any further questions.